Postage meter machines are commercially available in a number of variations. A printing rotor which comprises a postage value stamp on its cylindrical surface is standard in these machines. The numerals on this value stamp are selectively movable and are set by the user according to the postage required in each case. A counter or meter amount storage, in which all meter amounts and postage amounts are added up so that they can be accounted for by the authorized postal authority, is coupled with the postage value stamp. In addition, a place and date stamp, an advertizing stamp and possibly other stamps are arranged on the cylinder surface of the printing rotor and can be set as desired.
In metering, the printing rotor rolls over the postal item to be metered, e.g. a letter, making a complete revolution and in so doing imprints the various stamps one after the other. Such a postage meter machine is described for example in Hasler Mitteilungen [Hasler Review] 37 (Apr. 1978), No. 1, pages 1-7 (R. Grunig: Die Frankiermaschine Hasler Mailmaster [The Hasler Mailmaster Postage Meter Machine]).
In the past, the postage value stamp was generally adjusted via toothed racks which are supported in the shaft of the printing rotor so as to be displaceable in the longitudinal direction of this shaft and constitute part of a working connection between the value stamp and the meter amount storage. Patent CH 160 586 is referred to in this regard by way of example.
A newer postage meter machine is known from U.S. Pat. No. 4,702,164 in which the postage amounts are set without the aid of toothed racks of the aforementioned type. This postage meter machine has a printing rotor which is supported on its shaft so as to be rotatable. The printing rotor and the adjusting means therein can be connected in three different ways by means of a positioning rod, which is displaceable in the longitudinal direction, and by other means. Accordingly, three different modes of operation can be adjusted. In the "value select" or "digit select" operating mode, a printing wheel is rotated into a desired adjusting position while the rotor remains stationary, thereby setting a number to be imprinted. In the "print wheel select" (bank select) operating mode, the next print wheel to be set is mechanically coupled with the shaft while the rotor again remains stationary. Finally, in the third operating mode, "print", the rotor is rigidly coupled with the shaft in the conventional sense and the desired metering is effected in that the rotor rolls over the postal item running through it.
The shafts of all of the aforementioned postage meter machines are relatively complicated, and accordingly costly parts which can generally be produced only by chip-removing machining.